1. Field of the Invention
The present invention relates to a method for controlling an information processing system and to an information processing system.
2. Related Background Art
Disaster recovery in information processing systems is drawing attention. As a technology to realize disaster recovery, a technology for performing dual writing without the intervention of host computers among a plurality of storage apparatuses installed at physically remote sites (this technology is hereinafter called “remote copy”) is known. In remote copy, a first storage apparatus and a second storage apparatus are each connected through a dedicated telephone line or public telephone line. The second storage apparatus, which is a replication destination storage apparatus, has a logical volume that corresponds to a replication source logical volume of the first storage apparatus, which is a replication source storage apparatus, and data in the logical volume of the first storage apparatus is controlled to be written to the logical volume of the second storage apparatus. Through such control, when there is an update of data in the first storage apparatus from a host computer, the updated data is written to the first logical volume, as well as to the second logical volume. In this way, redundancy of data in the logical volume of the first storage apparatus and the second storage apparatus is managed according to the remote copy technology.
According to this mechanism, even if the first storage apparatus becomes unusable due to natural disasters such as earthquake and flood, or to man-made disasters such as fire and terrorism, the logical volume of the second storage apparatus can be used to quickly resume business operations.
However, the remote copy fails to function when data cannot be written to the replication destination logical volume. As a result, duplicated data state, in which data is in both the replication source logical volume and the replication destination logical volume, cannot be maintained until the replication destination logical volume recovers, which reduces the degree of redundancy provided for data in the replication source logical volume.